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Molecular characterization and gene expression of apolipophorin III from the ghost moth, Thitarodes pui (Lepidoptera, Hepialidae)
Author(s) -
Sun Zixuan,
Yu Junfeng,
Wu Wenjing,
Zhang Guren
Publication year - 2012
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20456
Subject(s) - biology , entomopathogenic fungus , hemolymph , instar , larva , botany , biological pest control , beauveria bassiana
Apolipophorin III (apoLp‐III) functions in lipid transport and immune activation in insects. We cloned a cDNA encoding putative apoLp‐III from larvae of Thitarodes pui , a host species of Ophiocordyceps sinensis , with great economic importance in the Tibetan Plateau. Excluding a putative signal peptide of the first 20 amino acid residues, the 171‐residue mature apoLp‐III has a calculated molecular mass of 18,606 Da. T. pui apoLp‐III shares little sequence homologies (<36%) with other apoLp‐IIIs. Phylogenetic analysis reveals that T. pui apoLp‐III belongs to a distinct, early diverging lineage of lepidopteran apoLp‐IIIs. Homology modeling of T. pui apoLp‐III shows a bundle of five amphipathic α‐helices, including a short helix 3′. T. pui apoLp‐III was constitutively expressed in larval fat body at lower levels than pupal and adult fat body. Significant induction of apoLp‐III expression, associated with strongest nodulation response, was observed in both sixth and eighth instar larvae challenged with Beauveria bassiana conidia at 1 hr after inoculation, compared with saline‐injected controls. The inoculation experiment as well as previous field studies revealed the relative susceptibility of the sixth instar to the entomopathogenic fungus. ApoLp‐III transcripts in the infected sixth and eighth instars were found to be induced highest 2‐ and 14.7‐fold, respectively, during the first 12 hr. In late‐stage infection, the infected susceptible sixth instar showed decrease in apoLp‐III expression followed by production of B. bassiana hyphal bodies, whereas the infected eighth instar showed longer lasting increase in the expression. These results suggest that apoLp‐III might contribute to T. pui immune response against fungal pathogens. © 2011 Wiley Periodicals, Inc.